1. Technical Field
The present invention relates to a substrate for a semiconductor device in which a contact hole is provided in a laminated structure on the substrate and that is used for an electro-optical device, such as a liquid crystal device or the like, to a method of manufacturing the substrate for a semiconductor device, to a substrate for an electro-optical device that has such a substrate for a semiconductor device, to an electro-optical device that has such a substrate for an electro-optical device, and to an electronic apparatus, such as a projector, or the like.
2. Related Art
In Japanese Unexamined Patent Application Publication No. 8-227939, a substrate for a semiconductor device in which a multi-layered wiring line is formed using a stack contact is disclosed. Further, in Japanese Unexamined Patent Application Publication No. 2002-108244, an electro-optical device that has such a substrate for a semiconductor device is disclosed. In the electro-optical device, a driving circuit that drives a plurality of pixel portions formed in an image display region on the substrate is formed in a peripheral region disposed in the periphery of the image display region. In the driving circuit, a stack contact which connects a semiconductor layer of a thin film transistor serving as a circuit element to a wiring line is formed to pass through, for example, a two-layered interlayer insulating film. More specifically, a contact hole has a first hole formed in an upper interlayer insulating film from the two-layered interlayer insulating film and a second hole formed to pass through a lower interlayer insulating film from the bottom of the first hole. Then, in the contact hole, a conductive material is continuously film-formed from the surface of the upper interlayer insulating film so as to form the wiring line. At this time, a portion of the wiring line formed in the contact hole is formed so as to serve as a stack contact. Through such a stack contact, a source and a drain of the thin film transistor are electrically connected to the wiring line.
Here, in the design of the thin film transistor, the ratio between the channel length and the channel width of the thin film transistor may be adjusted so as to increase mobility. Further, a plurality of stack contacts may be formed with respect to the source and the drain of the thin film transistor. Thus, the parasitic capacitance of the thin film transistor can be reduced and the on current can be increased.
With respect to adjacent contact holes from the plurality of contact holes formed in the semiconductor layer, the wiring line may be continuously formed from one contact hole to other contact holes, such that the plurality of contact holes can be electrically connected to one another. Accordingly, the wiring line for electrically connecting the plurality of contact holes to one another becomes relatively long. For this reason, when an electro-optical device is driven, the contact resistance between a part of the wiring line formed in the contact hole or another part of the wiring line formed on the surface of the interlayer insulating film and the interlayer insulating film and the contact resistance of the wiring line to the semiconductor layer in the contact hole may be relatively large. As such, if the contact resistance is increased, only some of the plurality of stack contacts may be electrically connected. As a result, the on current may be decreased.
Accordingly, in order to solve this inconsistency, the wiring line preferably has a width sufficient to cover all contact holes as viewed from the substrate surface in plan view. Thus, a current path having low contact resistance can be ensured in portions excluding the contact holes. In this case, however, when the driving circuit is reduced in size by narrowing the pitch of the wiring line, an interlayer insulating film that electrically isolates the wiring line from an additional conductive layer formed above the wiring line may be cracked. Thus, there may be a problem in that the yield in manufacturing an electro-optical device is degraded.